/*
 *  Copyright 2013 National Institute of Advanced Industrial Science and Technology
 *  
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *  
 *      http://www.apache.org/licenses/LICENSE-2.0
 *  
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.sss.util;

import java.text.DateFormat;
import java.util.Date;

public class StopWatch {
  private long    start;
  private long    stop;
  private boolean stopped = false;

  private StopWatch() {}

  /**
   * Creates new inctance using current time as starting point.
   */
  public static StopWatch start() {
    StopWatch sw = new StopWatch();

    sw.start = System.currentTimeMillis();
    sw.stop  = 0;

    return sw;
  }

  /**
   * Gets elapsed time from starting point.
   */
  public long getElapsedMillis() {
    if (!stopped) {
      throw new IllegalStateException("Stop watch already has been stopped.");
    }
    return stop - start;
  }

  /**
   * Gets elapsed time from starting point and stops.
   */
  public void stop() {
    stopped = true;
    stop = System.currentTimeMillis();
  }

  @Override
  public String toString() {
    StringBuilder sb = new StringBuilder();
    DateFormat df = DateFormat.getDateTimeInstance();

    sb.append(df.format(new Date(start)));
    sb.append(" - ");

    if (stopped) {
      sb.append(df.format(new Date(stop)));
      sb.append(" (");
      sb.append(getElapsedMillis());
      sb.append(" ms)");
    }

    return sb.toString();
  }
}
